CO2 gasification of birch char and the effect of CO inhibition on the calculation of chemical kinetics

Reactivity experiments have been performed in a TGA in the temperature range from 750 °C to 950 °C in steps of 50 °C. The CO2 partial pressure has been 0.05, 0.1, 0.2, 0.5 and 1.0 bar. Reactivity profiles have been obtained as a function of conversion for all temperatures and partial pressures and kinetic expressions have been calculated. An important feature of this investigation is that it compares the chemical kinetics according to two models: nth order kinetics and Langmuir-Hinshelwood kinetics. The nth order model is widely used and allows comparison among researchers since more results are available. The activation energy obtained according to nth order kinetics is 215 kJ/mol, the frequency factor 3.1106 and the reaction order 0.38. Since the nth order model does not include the effect of CO inhibition, the parameters for Langmuir-Hinshelwood kinetics have also been obtained. In spite of the large discrepancies for these kinetic parameters among researchers, the model fits very well the experimental data presented here. The ratio CO/CO2 appears to be a relevant factor for reactivity.